In the early 1980s, when I studied anthropology, human fossils older than about four million years amounted to a few inscrutable scraps. Just as accumulating molecular evidence from humans and apes pointed to the period between four million to six million years ago as the likely time frame for when we and they last shared a common ancestor, the fossil side of the story abruptly ended. What a difference a decade makes.

With the discovery in 1992 and 1993 of 17 specimens from Ethiopia later described as the new genus and species Ardipithecus ramidus, an early fossil rec-ord began to emerge. New fossils, both slightly younger and much older than the 4.4-million-year-old ramidus remains, soon followed. And with new fossils came new names and competing claims for being the oldest demonstrable human ancestor, or hominid. Besides Ardipithecus, Orrorin (in 2000) and Sahelanthropus (in 2002) sought their place on the hominid roll call with the more familiar fossils of Australopithecus and Homo. As veteran Science magazine correspondent Ann Gibbons quips, "The human story was beginning to look as complicated as a Tolstoy novel, with new characters appearing unexpectedly as the book of life unfolded."

In The First Human, Gibbons provides the first popular account of these intriguing discoveries and of rivalry and collaboration among the discoverers. An engrossing, fast-paced read, her story unfolds in many remote and rugged locales, from the Middle Awash of Ethiopia to the Tugen Hills of Kenya and the Djurab Desert of Chad.

Gibbons tells of hard-driven, dedicated teams contending with extreme heat, blowing sand, illness and other hazards of fieldwork in Africa, where success demands years, or decades, of persistence. After all, hominids may not have been common creatures in their day, and only fortuitous circumstances of gentle, rapid burial in suitable sediments kept a carcass from being a carnivore's meal, allowing it perchance to fossilize.

Gibbons seems as interested--if not more so--in personalities and politics as in the identities and significance of her protagonists' fossils. She is not the first to recognize that conflict as well as camaraderie accompanies the quest for human origins, and the scientists she portrays do possess the stuff of dramatic characters. There is the meticulous, mercurial paleontologist Tim White, co-leader of an international team with an unparalleled track record of spectacular discoveries, from the oldest modern human skull to one of the oldest human ancestors. And zoologist Meave Leakey, who has stepped out from the shadow of the most famous surname in human origins research to make singular contributions of her own. And Michel Brunet, a French expert on ancient hoofed mammals, inspired by Charles Darwin and Louis Leakey to pursue hominids.

Brunet bucked the odds by not looking for fossils in the celebrated cradle of humankind, East Africa's Rift Valley. He went to Chad, which hinted at its human fossil potential as early as 1961. Another hominid would not come to light there until 1995, but Brunet's team found that australopithecine jawbone and then explored much older sites. In 2001 a Chadian student on Brunet's team unearthed the cranium nicknamed "Touma¿." Formally named Sahelanthropus tchadensis, it is currently the oldest known hominid skull and pushes the emergence of our evolutionary line as far back as seven million years ago--as Gibbons writes, "so ancient that Brunet said that Touma¿ could 'touch with its finger' the last ancestor shared by humans and chimpanzees."